Add image resizing and variants to strapi upload in your strapi admin, change extensions/file-upload settings to Local upload resize
cd strapi project /plugins/upload
npm i strapi-provider-upload-local-resize
node resizing library https://www.npmjs.com/package/jimp
make sure the attributes 'url' and 'thumb exists in your in
plugins/uploads/models/File.settings.json
No UI fields yet, but feel free to change the lib/index.js to add variants or change sizes